This invention relates to compositions containing a pair of metal compounds distributed interactively on a deboronated HAMS-1B crystalline borosilicate molecular sieve (DBH) and a process of using such compositions as oxidation or oxidative dehydrogenation catalysts. More particularly, this invention relates to an improved process and composition for the alkyl group oxidation or oxidative dehydrogenation of an alkyl-substituted aromatic using a novel metal-compound-containing composition based upon a deboronated HAMS-1B crystalline borosilicate molecular sieve. Still more particularly, this invention relates to improved process for the methyl group oxidation of a methyl-substituted aromatic, such as p-xylene, to an aromatic mono and/or dialdehyde using a catalytic amount of a novel composition containing an iron molybdenum material distributed interactively on a deboronated HAMS-1B crystalline borosilicate molecular sieve.
U.S. Pat. No. 3,597,485 discloses a process for preparation of terephthalaldehyde (referred to herein as TPAA) which comprises subjecting p-xylene to a vapor phase oxidation in the presence of a catalyst mixture consisting of tungsten and molybdenum compounds.
U.S. Pat. No. 3,845,137 describes a process for preparation of TPAA in which p-xylene is oxidized in the vapor phase in the presence of a supported catalyst mixture of oxides of tungsten and molybdenum and at least a third metal or oxide selected from the group consisting of calcium, barium, titanium, zirconium, hafnium, thallium, niobium, zinc, and tin. According to this patent, the three component catalyst composition processes have improved catalyst life when compared to the catalyst described in U.S. Pat. No. 3,597,485. However, in both of these patents the conversion of p-xylene to TPAA is low.
U.S. Pat. No. 4,017,547 describes an improved process for making TPAA which uses a mixture of molybdenum oxide and silico-tungstic acid in combination with bismuth oxide. Catalyst lifetime and conversion to TPAA are both said to be improved over the prior art techniques. Not only is the conversion of p-xylene to TPAA said to be increased substantially by the use of the oxide of bismuth, but catalyst life is also said to be improved considerably, thereby permitting the operation of the oxidation process for longer periods of time before catalyst regeneration is required.
In an article entitled "Polymer Applications of Some Terephthalaldehyde Derivatives" in Ind. & Eng. Chem., Prod. Res. Dev. 15 (1) 83-88(1976), the authors use a tungsten-molybdenum catalyst in a ratio of about 9:1 deposited in an amount of ten percent or less on an alumina support to oxidize a mixture of air and p-xylene at 475.degree. C. to 575.degree. C. to a mixture of tolualdehyde (TAL) and TPAA. A 40-60% yield of TPAA with a minor production of byproducts is reported. The lifetime of the catalyst however appears to be poor.
Two catalyst properties are of primary importance for the operation of a continuous oxidation or oxidative dehydrogenation process which converts alkanes, aromatics or alkyl aromatics on a commercial scale. The first is yield of the desired oxidation product and the second is catalyst lifetime.
Now it has been discovered that metal-compound-containing compositions based on a deboronated HAMS-1B crystalline borosilicate molecular sieve having the MFI crystal structure can be very selective in oxidation and oxidative dehydrogenation reactions while having a long lifetime. For example, the alkyl group oxidation of an alkyl-substituted aromatic in the presence of a catalytic amount of a composition which is an iron molybdenum material distributed interactively on a deboronated HAMS-1B crystalline molecular sieve can yield aromatic aldehydes where the alkyl substituent is methyl and alkenyl-substituted aromatics when the alkyl substituent is larger than methyl. (oxidative dehydrogenation). The compositions give a combination of both good yield and good catalyst lifetime for the production of aromatic aldehydes or alkenyl aromatic products with reduced amounts of burning to fully oxidized products. In addition, the compositions show a selectivity in the oxidation of xylene and dialdehydes which can serve as the basis for a process for separating p-xylene from the other xylene isomers by selectively oxidizing p-xylene. Products of such selective p-xylene and dialdehyde oxidation are suitable intermediates for a variety of novel and specialty polymer applications including liquid crystals, engineering polymers, and optical brighteners. These oxidation products are also useful in synthesis of alcohols such as cyclohexanedimethanol. A particularly useful product of this invention is p-tolualdehyde which is useful as a feed to a water-based oxidation process to make purified terephthalic acid.